1) Field of the Invention
The present invention is directed to a method and system for the deployment and retrieval of linear arrays off of Unmanned Surface Vehicles (USVs).
2) Description of Prior Art
Sonar systems are used to determine the direction of propagating underwater signals and hence the location of the source of these signals. Sonar systems utilize arrangements or arrays of sources and receivers to detect arriving signals and to determine the direction from which these signals originated. For example, appropriate time delays applied to the receivers serve to steer the array and to calculate the direction of arrival of the incoming signals.
Some such systems are known generally as towed arrays and are towed behind surface ships, submarines and Unmanned Undersea Vehicles (UUVs). Unmanned Surface Vehicles (USVs) are currently being developed to perform a variety of missions including deploying and retrieving linear acoustic arrays. USVs are relatively small craft with lengths ranging from approximately 7 to 11 meters.
Handling systems on USVs must fit within tight space and conform to weight limits. Current USV handling systems for towed systems (including linear arrays) store the towed array on the deck of the USV and utilize a mechanical over-boarding system to deploy the towed array. The over-boarding system includes a winch located on deck to handle the cable and some type of over-boarding mechanism to get the array in and out of the water. The mechanism also includes some type of traction winch or mechanism to pull the array off the winch drum and into the water for deployment.
Since the towed array is similar to a flexible rope that is constructed to be pulled, the towed array cannot be very easily pushed. Therefore, an ideal method of deploying a flexible array is to have the array pulled off the craft and into the water. Once a sufficient length of the array is in the water, the hydrodynamic drag of the array towed through the water, combined with the array and cable weight, will pull the remaining array and cable off the winch.